The present invention relates to a method and apparatus for welding the enclosure for a semiconductor chip whereby the contents of the chip are protected against heat damage as the welding method forms a hermetically sealed joint along the marginal edges of the case and cover for the chip.
Vital to the proper protection of a semiconductor chip is the of provision of a hermetic seal between the case and the cover which enclose the chip. Made from metal or other fusible material, the case and cover are normally welded together by resistance welding which creates high temperatures because of the heat of the welding current. By use of conventional equipment and methods, the heat, transmitted across the case, oftentimes causes extensive damage to the components of the integrated circuit or other electrical parts and the semiconductor materials contained in the case.
We provide a solution to the problem by locating aligned electrodes directly below and above the case and its cover so that the heat which is generated by the welding current travels only along a relatively narrow path from the cover, traversing the side wall of the case rather than dissipating during and after each weld cycle across the contents of the case from side to side thereof.
The chip package and a special carrier therefor are clamped between the electrodes during each welding step and a drive is provided to index the package forwardly after each impulse. A template on the carrier serves as a guide to assure proper location of the package relative to the electrodes.